Patent Application
20240332427
This application claims the benefit of priority to Japanese Patent Application No. 2023-058228, filed on Mar. 31, 2023, the entire contents of which are incorporated herein by reference.
An embodiment of the present invention relates to a semiconductor device. Specifically, an embodiment of the present invention relates to a semiconductor device using an oxide semiconductor as a channel. In addition, an embodiment of the present invention relates to a method of manufacturing a semiconductor device.
In recent years, a semiconductor device in which an oxide semiconductor instead of amorphous silicon, low-temperature polysilicon, and single-crystal silicon is used for a channel has been developed (for example, Japanese laid-open patent publication No. 2021-141338, Japanese laid-open patent publication No. 2014-099601, Japanese laid-open patent publication No. 2021-153196, Japanese laid-open patent publication No. 2018-006730, Japanese laid-open patent publication No. 2016-184771, and Japanese laid-open patent publication No. 2021-108405). The semiconductor device in which an oxide semiconductor is used for a channel can be formed in a simple construction and low-temperature process, similar to a semiconductor device in which amorphous silicon is used for a channel. The semiconductor device in which an oxide semiconductor is used for a channel is known to have higher mobility than the semiconductor device in which amorphous silicon is used for a channel.
A semiconductor device according to an embodiment of the present invention includes a gate electrode, a gate insulating layer over the gate electrode, a metal oxide layer over the gate insulating layer, an oxide semiconductor layer having a polycrystalline structure over the metal oxide layer, a source electrode and a drain electrode over the oxide semiconductor layer, and an interlayer insulating layer in contact with the oxide semiconductor layer, the interlayer insulating layer covering the source electrode and the drain electrode, wherein the oxide semiconductor layer includes a first region overlapping one of the source electrode and the drain electrode and a second region in contact with the interlayer insulating layer, and a difference between a thickness of the first region and a thickness of the second region is 5 nm or less.
A method of manufacturing a semiconductor device to an embodiment of the present invention includes method of forming a gate electrode, forming a gate insulating layer over the gate electrode, forming a metal oxide film over the gate insulating layer, forming an oxide semiconductor layer having a polycrystalline structure over the metal oxide film, forming a metal oxide layer using the oxide semiconductor layer as a mask to etch the metal oxide film, depositing a conductive film over the oxide semiconductor layer, patterning the conductive film by etching to form a source electrode and a drain electrode, and forming an interlayer insulating layer in contact with the oxide semiconductor layer, the interlayer insulating layer covering the source electrode and the drain electrode, wherein the oxide semiconductor layer includes a first region overlapping one of the source electrode and the drain electrode and a second region in contact with the interlayer insulating layer, and a difference between a thickness of the first region and a thickness of the second region is 5 nm or less.
Hereinafter, embodiments of the present invention are described with reference to the drawings. The following invention is merely an example. A configuration that can be easily conceived by a person skilled in the art by appropriately changing the configuration of the embodiment while keeping the gist of the invention is naturally included in the scope of the present invention. In order to make the description clearer, the drawings may schematically show the widths, film thicknesses, shapes, and the like of the respective portions in comparison with the actual embodiments. However, the illustrated shapes are merely examples, and do not limit the interpretation of the present invention. In the present specification and the drawings, the same reference signs are given to elements similar to those described previously with respect to the above-described drawings, and detailed description thereof may be omitted as appropriate.
The “semiconductor device” refers to an overall device that can function by utilizing semiconductor characteristics. A transistor and a semiconductor circuit are one form of a semiconductor device. For example, the semiconductor device may be, an integrated circuit (IC) such as a display device or a micro-processing unit (MPU), or a transistor used in a memory circuit.
The “display device” refers to a structure that displays an image using an electro-optic layer. For example, the term “display device” may refer to a display panel that includes the electro-optic layer, or may refer to a structure with other optical members (for example, a polarized member, a backlight, a touch panel, and the like) attached to a display cell. The “electro-optic layer” may include a liquid crystal layer, an electroluminescent (EL) layer, an electrochromic (EC) layer or an electrophoretic layer, unless there is no technical contradiction. Therefore, although a liquid crystal display device including a liquid crystal layer and an organic EL display device including an organic EL layer are exemplified as a display device in the following embodiments, the structure according to the present embodiment can be applied to a display device including the other electro-optic layers described above.
A direction from a substrate toward an oxide semiconductor layer is referred to as upper or above in each embodiment of the present invention. Conversely, a direction from the oxide semiconductor layer to the substrate is referred to as lower or below. For convenience of explanation, the phrases “above” or “below” are used for description, but for example, the substrate and the oxide semiconductor layer may be arranged so that the vertical relationship is reversed from that shown in the drawings. In the following explanation, for example, the expression “an oxide semiconductor layer on a substrate” merely describes the vertical relationship between the substrate and the oxide semiconductor layer as described above, and another member may be arranged between the substrate and the oxide semiconductor layer. The terms “above” or “below” mean a stacking order in which a plurality of layers is stacked, and may have a positional relationship in which a transistor and a pixel electrode do not overlap in a plan view when expressed as a pixel electrode above a transistor. On the other hand, in the case of expressing a pixel electrode vertically above a transistor, it means a positional relationship in which the transistor and the pixel electrode overlap in a plan view. In addition, a plan view refers to viewing from a direction perpendicular to a surface of the substrate.
The terms “film” and “layer” can optionally be interchanged with one another in this specification and the like.
The expression “α includes A, B, or C,” “a includes any of A, B, or C,” “α includes one selected from a group consisting of A, B and C,” and the like does not exclude the case where α includes a plurality of combinations of A to C unless otherwise specified, in this specification and the like. Furthermore, these expressions do not exclude the case where a includes other elements.
In addition, the following embodiments can be combined as long as there is no technical contradiction.
A semiconductor device 10 according to an embodiment of the present invention is described with reference to
A configuration of the semiconductor device 10 according to an embodiment of the present invention is described with reference to
The semiconductor device 10 is arranged above a substrate 11 as shown in
Although a bottom-gate transistor is exemplified as the semiconductor device 10 in the present embodiment, the semiconductor device 10 is not limited to the bottom-gate transistor. For example, the semiconductor device 10 may be a dual-gate transistor in which the gate electrode is arranged above and below the oxide semiconductor layer 26.
The gate electrode 12GE is arranged above the substrate 11. The gate insulating layers 14 and 16 are arranged above the substrate 11 and the gate electrode 12GE. The gate insulating layers 14 and 16 have a stacked structure. The metal oxide layer 28 is arranged above the gate insulating layer 16. The oxide semiconductor layer 26 is arranged above the metal oxide layer 28. The source electrode 32S and the drain electrode 32D are arranged above the oxide semiconductor layer 26. The interlayer insulating layers 34 and 38 are arranged above the oxide semiconductor layer 26, the source electrode 32S, and the drain electrode 32D. The interlayer insulating layers 34 and 38 have a stacked structure and the interlayer insulating layer 38 is arranged above the interlayer insulating layer 34. That is, the interlayer insulating layers 34 and 38 cover the source electrode 32S and the drain electrode 32D, and the interlayer insulating layer 34 is in contact with the oxide semiconductor layer 26.
The oxide semiconductor layer 26 overlaps the gate electrode 12GE in a plan view as shown in
A planar pattern of the metal oxide layer 28 is substantially the same as a planar pattern of the oxide semiconductor layer 26 in a plan view as shown in
A wiring 12W and a wiring 32W function as a gate wiring. The wiring 32W is electrically connected to the wiring 12W via a contact hole 15. Although details are described later, the wiring 12W is formed as the same layer as the gate electrode 12GE. In addition, the wiring 32W is formed as the same layer as the source electrode 32S and the drain electrode 32D. Further, the wiring 32W may not be arranged above the wiring 12W.
The oxide semiconductor layer 26 has light transmittance and has a polycrystalline structure containing a plurality of grains. Although details are described later, the oxide semiconductor layer 26 having the polycrystalline structure can be formed by using a Poly-OS (Polycrystalline Oxide Semiconductor) technique. Therefore, the oxide semiconductor included in the oxide semiconductor layer 26 may be described as Poly-OS hereinafter.
A particle diameter of the crystal grain contained in Poly-OS is 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.5 μm or more. For example, the particle diameter of the crystal grain can be obtained using a cross-sectional SEM observation, a cross-sectional TEM observation, or an electron back scattered diffraction (EBSD) method.
Since the particle diameter of the crystal grain included in Poly-OS is 0.1 μm or more as described above, there is a region containing only one crystal grain along a thickness direction, in the oxide semiconductor layer 26 having a thickness of 10 nm or more and 30 nm or less.
Poly-OS has excellent etching resistance. Although details are described later, Poly-OS has excellent etching resistance against an etching solution or an etching gas used in forming the source electrode 32S and the drain electrode 32D. Therefore, the oxide semiconductor layer 26 is hardly etched when forming the source electrode 32S and the drain electrode 32D. Therefore, a thickness of the first region of the oxide semiconductor layer 26 overlapping the source electrode 32S or the drain electrode 32D (that is, the source region or the drain region) is substantially the same as a thickness of the second region of the oxide semiconductor layer 26 not overlapping the source electrode 32S and the drain electrode 32D (that is, the channel region). In other words, the difference between the thickness of the first region and the thickness of the second region is 5 nm or less, preferably 3 nm or less, and more preferably 1 nm or less.
The thickness of the channel region affects the electrical characteristics of the semiconductor device. If the variation in the thickness of the channel region is large, it is not possible to provide a semiconductor device having stable electrical characteristics. That is, the yield of the semiconductor device decreases. On the other hand, the semiconductor device 10 has stable electrical characteristics because it is possible to control the thickness of the channel region of the oxide semiconductor layer 26. For example, it is possible to obtain a field-effect mobility (field-effect mobility in a linear region) in which the mobility is 20 cm2/Vs or more, and further, 30 cm2/Vs or more in a range where the channel length L of the channel region is 2 μm or more and 4 μm or less and the channel width of the channel region is 2 μm or more and 25 μm or less, in the semiconductor device 10.
A method of manufacturing the semiconductor device 10 according to an embodiment of the present invention is described with reference to
The gate electrode 12GE is formed on the substrate 11 in step S1001 (“GE formation”) of
A rigid substrate having light transmittance, such as a glass substrate, a quartz substrate, a sapphire substrate, or the like, is used as the substrate 11. If the substrate 11 needs to have flexibility, a polyimide substrate, an acryl substrate, a siloxane substrate, a fluororesin substrate, or the like, or a substrate containing resin, is used as the substrate 11. In the case where the substrate containing resin is used as the substrate 11, an impurity element may be introduced into the resin to improve the heat resistance of the substrate 11. In particular, in the case where the semiconductor device 10 is a top-emission display, the substrate 11 does not need to be transparent, so that an impurity that lowers the transmittance of the substrate 11 may be used. In the case where the display device 10 is used for an integrated circuit that is not a display device, a substrate without translucency such as a semiconductor substrate such as a silicon substrate, a silicon carbide substrate, or a conductive substrate such as a stainless substrate may be used as the substrate 11.
The gate electrode 12GE is formed by processing a conductive film formed by a sputtering method. A common metal material is used as the metal material of the gate electrode 12GE. For example, aluminum (Al), titanium (Ti), chromium (Cr), cobalt (Co), nickel (Ni), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), bismuth (Bi), silver (Ag), copper (Cu), and alloys thereof or compounds thereof are used as the gate electrode 12GE. The above-described metal materials may be used in a single layer or in a stacked layer as the gate electrode 12GE.
The gate insulating layers 14 and 16 are formed above the gate electrode 12GE in step S1002 (“GI formation”) of
The gate insulating layer 14 in which an insulating material containing nitrogen is used and the gate insulating layer 16 in which an insulating material containing oxygen is used are preferably formed in this order above the substrate 11. Using the insulating material containing nitrogen as the gate insulating layer 14 makes it possible to block impurities that diffuse from the substrate 11 toward the oxide semiconductor layer 26. In addition, using the insulating material containing oxygen as the gate insulating layer 16 makes it possible to release oxygen by a heat treatment. For example, a temperature of the heat treatment by which the insulating material containing oxygen releases oxygen is 500° C. or lower, 450° C. or lower, or 400° C. or lower. In addition, the insulating material containing oxygen may release oxygen when heated in any of the steps of the manufacturing process of the semiconductor device 10.
A thickness of the gate insulating layer 14 is preferably greater than a thickness of the gate insulating layer 16. For example, 300 nm of the silicon nitride is formed as the gate insulating layer 14 in the present embodiment. For example, 100 nm of the silicon oxide is formed as the gate insulating layer 16.
A metal oxide film 18 is deposited above the gate insulating layers 14 and 16 in step S1003 (“MO deposition”) of
A metal oxide containing aluminum as a main component is used as the metal oxide film 18. For example, an inorganic insulating layer such as aluminum oxide (AlOx), aluminum oxynitride (AlOxNy), aluminum nitride oxide (AlNxOy), or aluminum nitride (AlNx) is used as the metal oxide film 18. The metal oxide layer containing aluminum as a main component means that the ratio of aluminum contained in the metal oxide layer is 1% or more of the total amount of the metal oxide film 18. The ratio of aluminum contained in the metal oxide film 18 may be 5% or more and 70% or less, 10% or more and 60% or less, or 30% or more and 50% or less of the total amount of the metal oxide film 18. The ratio may be a mass ratio or a weight ratio.
For example, a thickness of the metal oxide film 18 is 1 nm or more and 10 nm or less, preferably 1 nm or more and 5 nm or less. Aluminum oxide is used as the metal oxide film 18 in the present embodiment. Aluminum oxide has a high barrier property against gases such as oxygen or hydrogen. In other words, the barrier property refers to a function of suppressing a gas such as oxygen or hydrogen from passing through the aluminum oxide. That is, even if a gas such as oxygen or hydrogen is present, the gas is not moved from the layer arranged below the aluminum oxide film to the layer arranged above the aluminum oxide film. Alternatively, even if a gas such as oxygen or hydrogen is present, the gas is not moved from the layer arranged above the aluminum oxide film to the layer arranged below the aluminum oxide film.
An oxide semiconductor film 22 is formed above the metal oxide film 18 in step S1004 (“OS deposition”) of
A metal oxide having semiconductor properties can be used as the oxide semiconductor film 22. For example, an oxide semiconductor containing two or more metal elements including indium (In) is used as the oxide semiconductor film 22. In addition, the proportion of indium in the two or more metal elements is 50% or more. Gallium (Ga), zinc (Zn), aluminum (Al), hafnium (Hf), yttrium (Y), zirconium (Zr), or a lanthanoid-based element is used as the oxide semiconductor film 22 in addition to indium. The oxide semiconductor film 22 preferably contains a Group 13 element. In addition, an element other than the above may be used as the oxide semiconductor film 22.
In the case where the oxide semiconductor film 22 is crystallized by the OS annealing described later, the oxide semiconductor film 22 after the deposition and before the OS annealing is preferably amorphous (a state in which the oxide semiconductor has few crystalline components). That is, the oxide semiconductor film 22 is preferably formed under a condition that the oxide semiconductor film 22 immediately after the deposition does not crystallize as much as possible. For example, in the case where the oxide semiconductor film 22 is formed by a sputtering method, the oxide semiconductor film 22 is formed while controlling the temperature of an object to be deposited (the substrate 11 and the structure formed thereon).
Since ions generated in a plasma and atoms recoiled by a sputtering target collide with the object to be deposited when deposition is performed on the object to be deposited by the sputtering method, the temperature of the object to be deposited increases with the deposition treatment. When the temperature of the object to be deposited during the deposition treatment increases, microcrystals are contained in the oxide semiconductor film 22 immediately after the deposition. When the oxide semiconductor film 22 contains microcrystals, the particle diameter cannot be increased by subsequent OS annealing. For example, in order to control the temperature of the object to be deposited, the deposition can be performed while cooling the object to be deposited. For example, the object to be deposited can be cooled from the surface opposite to the depositing surface so that the temperature of the depositing surface of the object to be deposited (hereinafter, referred to as “deposition temperature”) is 100° C. or lower, 70° C. or lower, 50° C. or lower, or 30° C. or lower. In particular, the deposition temperature of the oxide semiconductor film 22 is preferably 50° C. or lower. Forming the oxide semiconductor film 22 while the substrate 11 is cooled makes it possible to obtain the oxide semiconductor film 22 with few crystalline components immediately after the deposition.
The oxide semiconductor film 22 having an amorphous structure is deposited under the condition of an oxygen partial pressure of 10% or less, in the sputtering process. When the oxygen partial pressure is high, the oxide semiconductor film 22 immediately after the deposition contains microcrystals due to excessive oxygen contained in the oxide semiconductor film 22. Therefore, the oxide semiconductor film 22 is preferably deposited under the condition that the oxygen partial pressure is low. For example, the oxygen partial pressure is 1% or more and 5% or less, preferably 2% or more and 4% or less. The distribution of oxygen in the deposition apparatus tends to be uneven under the condition that the oxygen partial pressure is less than 1%. As a result, the composition of oxygen in the oxide semiconductor film is also uneven, and the oxide semiconductor film containing a large amount of microcrystals is formed, or the oxide semiconductor film that does not crystallize even if the OS annealing treatment is performed later is deposited.
A pattern of an oxide semiconductor layer 24 is formed in step S1005 (“OS pattern formation”) of
Forming the oxide semiconductor layer 24 having a predetermined pattern (that is, patterning of the oxide semiconductor film 22) is preferably performed before OS annealing. Poly-OS after OS annealing has high etching resistance and is difficult to be patterned by etching. In addition, damages (for example, oxygen defects in the oxide semiconductor layer 24) caused in forming the oxide semiconductor layer 24 can be repaired by OS annealing by performing OS annealing after the formation of the oxide semiconductor layer 24.
The oxide semiconductor layer 26 is formed by performing a heat treatment (OS annealing) on the oxide semiconductor layer 24 after the oxide semiconductor layer 24 is formed, in step S1006 (“OS annealing”) of
Field-effect mobility tends to be increased in a thin film transistor by increasing carriers by decreasing the thickness of the oxide semiconductor layer to reduce the effect of a back channel. That is, the thin film transistor tends to have higher field effect mobility as the thickness of a region functioning as the channel of the oxide semiconductor layer decreases. Therefore, the smaller the thickness of the oxide semiconductor layer, the better. However, the oxide semiconductor layer does not crystallize sufficiently even if the heat treatment is performed after the oxide semiconductor layer is formed to a thickness of 10 nm or less. If the oxide semiconductor layer is not sufficiently crystallized, the oxide semiconductor layer and the metal oxide layer disappear during the etching process for patterning the metal oxide layer using the oxide semiconductor layer as a mask.
In addition, the crystallinity of the oxide semiconductor layer 26 contributes to the improvement of the field effect mobility, in the thin film transistor. Therefore, the oxide semiconductor layer 26 preferably has the polycrystalline structure. However, if microcrystals are contained in the oxide semiconductor film 22, the particle diameter of the crystal grain of the polycrystalline structure cannot be increased even if the heat treatment is performed thereafter. It is difficult to achieve both thinning and good crystallization of the oxide semiconductor layer as described above.
The oxide semiconductor film 22 is deposited by a sputtering method at a low oxygen partial pressure of 3% or more and 5% or less. Forming the oxide semiconductor film 22 under the condition that the oxygen partial pressure is low makes it possible to suppress excessive oxygen from being contained in the oxide semiconductor film 22 and microcrystals from being contained in the oxide semiconductor film 22 immediately after the deposition. As a result, it is possible to suppress the growth of crystals from microcrystals during the heat treatment of the oxide semiconductor layer 24. Therefore, even if the oxide semiconductor film 22 is formed to have a thickness greater than 10 nm and 30 nm or less, the particle diameter of the crystal grain of the polycrystalline structure of the oxide semiconductor layer 26 can be increased.
The metal oxide film 18 is formed by patterning the metal oxide layer 28 as shown in step S1007 of
The contact hole 15 is formed in the gate insulating layers 14 and 16 in step S1008 of
The source electrode 32S, the drain electrode 32D, and the wiring 32W are formed in step S1009 (“SD formation” of
Patterning using wet etching or dry etching is performed in order to form the source electrode 32S, the drain electrode 32D, and the wiring 32W. An etching solution is used in the wet etching. For example, a solution containing at least two selected from a group consisting of phosphoric acid, acetic acid, nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, and oxalic acid can be used as the etching solution. Specifically, a mixed acid etching solution containing phosphoric acid, acetic acid, and nitric acid as main components can be used as the etching solution. In addition, a mixed solution of a hydrogen peroxide solution and ammonia solution (hereinafter referred to as “H2O2/NH3 solution”) can also be used as the etching solution. An etching gas is used in the dry etching. For example, a fluorine-containing gas such as a sulfur hexafluoride gas (SF6) (hereinafter, referred to as “fluorine-based gas”) or a chlorine-containing gas such as a chlorine gas (Cl2) (hereinafter, referred to as “chlorine-based gas”) is used as the etching gas.
Poly-OS has excellent etching resistance. Specifically, the etching rate for the etching solution or the etching gas used in forming the source electrode 32S and the drain electrode 32D is very small. This means that Poly-OS is hardly etched by the etching solution or etching gas. Therefore, even if a conductive film is directly deposited on the oxide semiconductor layer 26 and the source electrode 32S and the drain electrode 32D are formed by patterning the conductive film in the semiconductor device 10, the channel region of the oxide semiconductor layer 26 is hardly etched.
For example, the etching rate of the oxide semiconductor layer 26 with respect to the etching solution used in forming the source electrode 32S and the drain electrode 32D is 0.1 nm/sec or less, or 0.01 nm/sec or less. In addition, the etching rate of the oxide semiconductor layer 26 with respect to the etching gas used in forming the source electrode 32S and the drain electrode 32D is 0.5 nm/sec or less, or 0.1 nm/sec or less. For example, the etching rate of the oxide semiconductor layer 26 with respect to a chlorine-based gas used in forming the source electrode 32S and the drain electrode 32D is 0.3 nm/sec or less. For example, the etching rate of the oxide semiconductor layer 26 with respect to a fluorine-based gas used in forming the source electrode 32S and the drain electrode 32D is 0.1 nm/sec or less. In addition, the etching rate of etching using the chlorine-based gas is slightly higher than that of etching using an etching solution or the fluorine-based gas.
In the case where the etching is performed using the chlorine-based gas, the workability of the source electrode 32S and the drain electrode 32D is better than that of etching using an etching solution. Therefore, an etching solution or an etching gas may be selected as appropriate depending on a structure of the conductive film for forming the source electrode 32S and the drain electrode 32D.
In the case where the source electrode and the drain electrode are formed above the oxide semiconductor, the oxide semiconductor layer is also etched by etching the source electrode and the drain electrode in the semiconductor device using the oxide semiconductor having no polycrystalline structure such as IGZO. Specifically, the etching rate of IGZO with respect to the chlorine-containing gas is 1.0 nm/sec, and in view of the fact that the channel region is etched at this etching rate, the oxide semiconductor layer needs to be deposited thickly in advance. For example, in the case of manufacturing a semiconductor device in which the thickness of the channel region is 40 nm or less, an oxide semiconductor layer with a thickness of about 65 nm is formed and the etching time needs to be adjusted so that the thickness of the channel region is 40 nm or less when forming the source electrode and the drain electrode. However, it is difficult to control the thickness of the channel region by the etching time. In addition, precise control of the thickness of the channel region by etching time is difficult when the etching rate is high. In this case, the variation in the thickness of the channel region increases.
In addition, a concave portion is formed on the upper surface of the oxide semiconductor layer when the thickness of the channel region is greatly reduced. Although the interlayer insulating layer arranged above the oxide semiconductor layer is deposited so as to cover the concave portion, the interlayer insulating layer cannot sufficiently cover the concave portion when a depth of the concave portion is large. That is, a gap may be formed between the oxide semiconductor layer and the interlayer insulating layer or between the source electrode and drain electrode and the interlayer insulating layer. This can be a factor that causes variations in not only the electrical characteristics but also the reliability of the semiconductor device.
In contrast, the oxide semiconductor layer 26 having the polycrystalline structure can have 0.00 nm/sec to 0.1 nm/sec etching rates, preferably 0.00 nm/sec to 0.06 nm/sec, in both wet etching and dry etching. That is, the oxide semiconductor layer 26 having the polycrystalline structure has a lower etching rate and higher etching resistance than the oxide semiconductor layer using IGZO. Therefore, there is no need to consider film thinning caused by etching, and controllability is good. Therefore, the oxide semiconductor layer can be formed with a thin thickness larger than 10 nm and 30 nm or less. In addition, the selectivity of the conductive material that can be used as the source electrode 32S, the drain electrode 32D, and the wiring 32W is improved. For example, even when the conductive film using a stacked structure of MoW/Al/MoW or a single-layer structure of MoW is processed by wet-etching in order to form the source electrode 32S and the drain electrode 32D, it is possible to suppress the oxide semiconductor layer 26 from being reduced in thickness.
The etching rate of the oxide semiconductor layer 26 with respect to the etching solution used in forming the source electrode 32S and the drain electrode 32D is very small as described above. Therefore, the thickness of the first region (that is, the source region or drain region) of the oxide semiconductor layer 26 overlapping the source electrode 32S or the drain electrode 32D is substantially the same as the thickness of the second region (that is, the channel region) of the oxide semiconductor layer 26 not overlapping the source electrode 32S and the drain electrode 32D. In other words, the difference between the thickness of the first region and the thickness of the second region can be controlled to be 5 nm or less, preferably 3 nm or less, and more preferably 1 nm or less. That is, variations in the thickness of the channel region are suppressed.
The interlayer insulating layer 34 is deposited above the oxide semiconductor layer 26, the source electrode 32S, and the drain electrode 32D, in step 1010 (“SiOx formation”) of
The interlayer insulating layer 34 can be deposited using the same deposition method as the gate insulating layers 14 and 16. In order to increase the composition ratio of oxygen in the interlayer insulating layer 34, the film may be formed at a relatively low temperature (for example, a deposition temperature of less than 350° C.). In addition, the interlayer insulating layer 34 may be deposited at a deposition temperature of 350° C. or higher in order to form an insulating layer with few defects as the interlayer insulating layer 34. Further, an oxygen-implantation treatment may be performed on part of the interlayer insulating layer 34 after the interlayer insulating layer 34 is deposited.
A thickness of the interlayer insulating layer 34 is 50 nm or more and 300 nm or less, 60 nm or more and 200 nm or less, or 70 nm or more and 150 nm or less.
A metal oxide film 36 is deposited above the interlayer insulating layer 34 in step S1011 (“MO deposition”) of
A metal oxide containing aluminum as a main component is used as the metal oxide film 36. For example, an inorganic insulating layer such as aluminum oxide (AlOx), aluminum oxynitride (AlOxNy), aluminum nitride oxide (AlNxOy), or aluminum nitride (AlNx) is used as the metal oxide film 36. The metal oxide layer containing aluminum as a main component means that the ratio of aluminum contained in the metal oxide layer is 1% or more of the total amount of the metal oxide film 36. The ratio of aluminum contained in the metal oxide film 36 may be 5% or more and 70% or less, 10% or more and 60% or less, or 30% or more and 50% or less of the total amount of the metal oxide film 36. The ratio may be a mass ratio or a weight ratio.
A thickness of the metal oxide film 36 is 1 nm or more and 50 nm or less, preferably 1 nm or more and 30 nm or less. Aluminum oxide is preferably used as the metal oxide film 36. Aluminum oxide has a high barrier property against gas such as oxygen or hydrogen. In this case, the barrier property refers to a function of suppressing a gas such as oxygen or hydrogen from passing through the aluminum oxide. That is, it means that the gas such as oxygen or hydrogen in the layer arranged below the aluminum oxide film is not moved to the layer arranged above the aluminum oxide film. Alternatively, it means that the gas such as oxygen or hydrogen in the layer arranged above the aluminum oxide film is not moved to the layer arranged below the aluminum oxide film.
In addition, a metal oxide containing a metal other than aluminum as a main component may be used as the metal oxide film 36. For example, indium tin oxide (ITO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), or the like can be used as the metal oxide film 36.
A heat treatment is performed while the interlayer insulating layer 34 and the metal oxide film 36 are deposited above the oxide semiconductor layer 26 in step S1012 (“oxidation annealing”) of
Many oxygen defects occur in the oxide semiconductor layer 26 during the process from the deposition of the oxide semiconductor layer 26 to the deposition of the interlayer insulating layer 34 above the oxide semiconductor layer 26. However, the oxygen released from the interlayer insulating layer 34 is supplied to the oxide semiconductor layer 26 by the oxidation annealing of step S1012, and the oxygen defects are repaired.
The metal oxide film 36 is removed in step S1013 (“MO removal”) of
The interlayer insulating layer 38 is deposited above the interlayer insulating layer 34 in step S1014 (“SiNx deposition”) of
The semiconductor device 10 shown in
Excellent electrical characteristics with a mobility of 20 cm2/Vs or more and or more 30 cm2/Vs can be obtained in a range where the channel length of the channel region is 2 μm or more and 4 μm or less, and the channel width of the channel region is 2 μm or more and 25 μm or less, in the semiconductor device 10 manufactured by the above-described manufacturing method.
A thickness of the region acting as the channel in the oxide semiconductor layer 26 can be substantially reduced by the action of the metal oxide layer 28 by arranging the metal oxide layer 28 below the oxide semiconductor layer 26. As a result, it is possible to improve the mobility of the semiconductor device 10 because the density of carriers accumulated in the channel can be increased. The metal oxide film 18 has a gas barrier property against oxygen and hydrogen. However, if oxygen is not supplied from the gate insulating layers 14 and 16 to the oxide semiconductor layer 26 via the metal oxide layer 28, oxygen defects on the back surface of the oxide semiconductor layer 26 cannot be repaired. Therefore, the oxygen contained in the gate insulating layer 16 can be supplied to the back surface of the oxide semiconductor layer 26 as appropriate by setting the thickness of the metal oxide film 18 to 1 nm or more and 10 nm or less, preferably 1 nm or more and 5 nm or less.
In addition, even when the semiconductor device 10 is manufactured using a large-area substrate, variations in the shape of the oxide semiconductor layer 26 can be suppressed. Therefore, in-plane variations in the electrical characteristics of the semiconductor device 10 can be suppressed, and the yield can be improved.
A display device 20 using the semiconductor device 10 according to an embodiment of the present invention is described with reference to
A sealing region 240 where the sealing portion 310 is arranged is a region around the liquid crystal region 220. The FPC 330 is arranged in a terminal region 260. The terminal region 260 is a region where the array substrate 300 is exposed from the counter substrate 320 and is arranged outside the sealing region 240. The outside of the sealing region 240 means the region surrounded by the region where the sealing portion 310 is arranged and the outside of the sealing portion 310. The IC chip 340 is arranged above the FPC 330. The IC chip 340 supplies a signal for driving each pixel circuit 301.
A source wiring 304 extends from the source driver circuit 302 in the second direction D2 and is connected to the plurality of pixel circuits 301 arranged in the second direction D2. The gate electrode 12GE extends from the gate driver circuit 303 in the first direction D1 and is connected to the plurality of pixel circuits 301 arranged in the first direction D1.
A terminal portion 306 is arranged in the terminal region 260. The terminal portion 306 and the source driver circuit 302 are connected by a connecting wiring 307. Similarly, the terminal portion 306 and the gate driver circuit 303 are connected by the connecting wiring 307. The FPC 330 is connected to the terminal portion 306, an external device to which the FPC 330 is connected is connected to the display device 20, and each pixel circuit 301 arranged in the display device 20 is driven by a signal from the external device.
The semiconductor device 10 according to the first embodiment is used as a transistor included in the pixel circuit 301, the source driver circuit 302, and the gate driver circuit 303.
The gate electrode 12GE is arranged above the substrate 11 as shown in
The interlayer insulating layers 34 and 38 are arranged above the source electrode 32S and the drain electrode 32D. An insulating layer 39 is arranged above the interlayer insulating layers 34 and 38. The insulating layer 39 is arranged to reduce unevenness caused by the semiconductor device 10. A contact hole is formed in the interlayer insulating layers 34 and 38 and the insulating layer 39 so as to expose the upper surface of the source electrode 32S. A common electrode 42C arranged in common to a plurality of pixels is arranged above the insulating layer 39. An insulating layer 44 is arranged above the common electrode 42C. The insulating layer 44 is arranged inside the contact hole. Forming the insulating layer 44 with a silicon nitride film makes it possible to suppress moisture from entering from the contact hole via the insulating layer 44. A pixel electrode 46P is arranged above the insulating layer 44 and inside the contact hole. The pixel electrode 46P is connected to the drain electrode 32D.
In addition, a wiring 12C is arranged above the substrate 11 and is connected to a wiring 32C via the contact hole arranged in the gate insulating layers 14 and 16. The wiring 12C and the wiring 32C function as a capacitance wiring. In addition, an electrode 46C is arranged above the insulating layer 39 and inside the opening. The storage capacitor 350 is formed by the common electrode 42C, the insulating layer 44, and the electrode 46C.
Although a configuration in which the semiconductor device 10 is used for the pixel circuit 301 is exemplified in the present embodiment, the semiconductor device 10 may be used for a peripheral circuit including the source driver circuit 302 and the gate driver circuit 303.
The display device 20 using the semiconductor device 10 according to an embodiment of the present invention is described with reference to
The display device 20 includes a pixel electrode 390, a light-emitting layer 392, and a common electrode 394 (the light-emitting element DO) above the insulating layer 39, as shown in
Although the configuration in which the semiconductor device described in the first embodiment is applied to the liquid crystal display device and the organic EL display device has been exemplified in the second embodiment and the third embodiment, the semiconductor device may be applied to a display device (for example, a self-luminous display device or an electronic paper type display device other than the organic EL display device) other than these display devices. In addition, the semiconductor device 10 can be applied from a medium-sized display device to a large-sized display device without any particular limitation. Even when manufacturing using the large-area substrate, variations in the shape of the oxide semiconductor layer 26 in the semiconductor device 10 are small. Therefore, in the case where the semiconductor device 10 is applied to the display device 20, unevenness in display can be reduced. In addition, the yield in manufacturing the display device 20 can be improved.
A result of the etching resistance of the oxide semiconductor layer having the polycrystalline structure is described in this example.
Samples used in this example are described. The oxide semiconductor layer (Poly-OS) having 30 nm of the polycrystalline structure was formed on a silicon wafer. Next, a conductive film was formed on the oxide semiconductor layer. Four types of conductive films are used: MoW structure, MoW/Al/MoW structure, Ti structure, and Ti/Al/Ti structure.
A sample subjected to wet etching with the mixed acid etching solution, a sample subjected to wet etching with the H2O2/NH3 solution, and a sample subjected to dry etching with the fluorine-based gas were prepared for the conductive film and oxide semiconductor with the MoW structure. In addition, the “mixed acid AT-2F (product name)” manufactured by Rasa Industries, Ltd. was used as the mixed acid etching solution. The proportion of phosphoric acid in the mixed acid etching solution is about 65%. Further, the temperature of the mixed acid etching solution was set to 40° C. (with temperature adjustment) and the temperature of the H2O2/NH3 solution was set to 22° C. (without temperature adjustment, room temperature) when the samples were etched.
For the conductive film with the MoW/Al/MoW structure and the oxide semiconductor layer, a sample was wet-etched with the mixed acid etching solution.
A sample subjected to wet etching with the H2O2/NH3 solution, a sample subjected to dry etching with the fluorine-based gas, and a sample subjected to dry etching with the chlorine-based gas were prepared for the conductive film and oxide semiconductor layer with the Ti structure.
A sample of Ti subjected to wet etching with the H2O2/NH3 solution, a sample of Al subjected to wet etching with the mixed acid etching solution, a sample of Ti subjected to wet etching with the H2O2/NH3 solution, and a sample subjected to dry etching with the chlorine-based gas were prepared for the conductive film and oxide semiconductor layer with the Ti/Al/Ti structure.
Next, a sample used in a comparative example is described. 40 nm of an IGZO oxide semiconductor layer was deposited on a silicon wafer. Next, a conductive film was formed on the oxide semiconductor layer. The Ti structure was used as the conductive film. A sample of the conductive film and oxide semiconductor layer with the Ti structure subjected to dry etching with the chlorine-based gas was prepared.
The etching rates [nm/sec] of the polycrystalline oxide semiconductor layer relative to an estimated over-etching time after processing the various conductive films are shown in Table 1 as the examples.
The etching rate of the oxide semiconductor layer (IGZO) relative to the estimated over-etching time after processing the conductive film with the Ti structure was 1.00 nm/sec, as a comparative example.
It was shown that the oxide semiconductor layer having the polycrystalline structure has higher etching resistance than the amorphous oxide semiconductor layer (IGZO), as shown in Table 1. In addition, it was shown that the etching rate was 0.00 nm/sec to 0.06 nm/sec in the case of etching with the mixed acid etching solution, etching with the H2O2/NH3 solution, and etching with the fluorine-based gas. It was shown that even when etching is performed using the chlorine-based gas, it has a sufficiently high etching resistance compared to the oxide semiconductor layer (IGZO).
Next, a result of the electrical characteristics of the semiconductor device 10 manufactured according to the flowchart shown in
Samples A to H prepared as the semiconductor device 10 are described in Example 2. Step S1007 and step S1008 are omitted from the samples A to H in the flowchart shown in
The gate electrode 12GE was formed on the substrate and the gate insulating layers 14 and 16 were formed on the gate electrode 12GE. 3 nm of the aluminum oxide layer was formed as the metal oxide film 18 on the gate insulating layers 14 and 16, and 30 nm of the oxide semiconductor film 22 was formed on the metal oxide film 18. The oxide semiconductor layer 24 was formed by processing the oxide semiconductor film 22, and the polycrystalline oxide semiconductor layer 26 (Poly-OS) was formed by performing OS annealing at 350° C. to 450° C. In addition, the metal oxide layer 28 was formed by removing the metal oxide film 18 using the oxide semiconductor layer 26 as a mask.
The MoW/Al/MoW structure was formed as the conductive film on the oxide semiconductor layer 26, and the source electrode and the drain electrode were formed by performing wet etching on the conductive film using the mixed acid etching solution. Next, 10 nm of the aluminum oxide layer was formed as the metal oxide film 36 after the interlayer insulating layer 34 was formed, and the metal oxide film 36 was removed after performing oxidation annealing. Finally, the interlayer insulating layer 38 was formed on the interlayer insulating layer 34. When the thickness of the oxide semiconductor layer was measured after the sample A was formed, 1 nm was removed.
Samples B to H were formed by changing the structure and the condition of the etching method for forming the conductive film for forming the source electrode and drain electrode from those of Sample A.
Sample B was formed under the same conditions as Sample A except that the MoW structure was used as the conductive film.
Sample C was formed under the same conditions as Sample A except that the MoW structure was formed as the conductive film and the source electrode and the drain electrode were formed by performing dry etching on the conductive film using an SF6 gas and O2 gas. When the thickness of the oxide semiconductor layer was measured after Sample C was formed, 2 nm was removed.
Sample D was formed under the same conditions as Sample A except that the Ti structure was formed as the conductive film and the source electrode and the drain electrode were formed by performing dry etching on the conductive film using a CF4 gas and O2 gas. When the thickness of the oxide semiconductor layer was measured after Sample D was formed, 2 nm was removed.
Sample E was formed under the same conditions as Sample A except that the Ti/Al/Ti structure was formed as the conductive film and the source electrode and the drain electrode were formed by performing dry etching on the conductive film using a Cl2 gas.
Sample F was formed under the same conditions as Sample A except that the Ti structure was formed as the conductive film and the source electrode and the drain electrode were formed by performing dry etching on the conductive film using an H2O2/NH3 gas.
Sample G was formed under the same conditions as Sample A except that the Ti/Al/Ti structure was formed as the conductive film and the source electrode and the drain electrode were formed by performing wet etching on the conductive film using the H2O2/NH3 solution for Ti, the mixed acid etching solution for Al, and the H2O2/NH3 solution for Ti.
Sample H is a comparative example, and the formation methods are different from those of Samples A to G. The gate electrode was formed on the substrate, and the gate insulating layer was formed on the gate electrode. 95 nm of the oxide semiconductor layer (IGZO (111)) was formed on the gate insulating layer. The oxide semiconductor layer was formed by processing the oxide semiconductor layer, and OS annealing was performed at 350° C. to 450° C.
A stacked structure of Ti/AlSi/Ti is formed on the oxide semiconductor layer as the conductive layer, and the source electrode and the drain electrode were formed by performing dry etching on the conductive film using the Cl2 gas. Next, 50 nm of the aluminum oxide layer was formed as the metal oxide layer after the interlayer insulating layer was formed, and oxidation annealing was performed. In addition, the target thickness of the oxide semiconductor layer by dry etching was 60 nm.
Next, the electrical characteristics of Samples A to H were measured. The measurement conditions of the electrical characteristics of Samples A to H are as follows.
It was shown that Samples A to G having the polycrystalline oxide semiconductor layer (Poly-OS) have high mobility and good electrical characteristics, as shown in
Next, a result of the electrical characteristics of the semiconductor device 10 manufactured according to the flowchart shown in
A Sample I and a Sample J prepared as the semiconductor device 10 are described in Example 3. Step S1007 and step S1008 are omitted for the Sample I and the Sample J in the flowchart in
The gate electrode 12GE was formed above the substrate and the gate insulating layers 14 and 16 were formed above the gate electrode 12GE. 3 nm of the aluminum oxide layer was formed as the metal oxide film 18 above the gate insulating layers 14 and 16, and 30 nm of the oxide semiconductor film 22 was formed above the metal oxide film 18. The oxide semiconductor layer 24 was formed by processing the oxide semiconductor film 22, and the polycrystalline oxide semiconductor layer 26 was formed by performing OS annealing at 350° C. to 450° C. In addition, the metal oxide layer 28 was formed by removing the metal oxide film 18 using the oxide semiconductor layer 26 as a mask.
The MoW/Al/MoW structure was formed as the conductive film above the oxide semiconductor layer 26, and the source electrode and the drain electrode were formed by performing wet-etching on the conductive film using the mixed acid etching solution. Next, 10 nm of the aluminum oxide layer was formed as the metal oxide film 36 after the interlayer insulating layer 34 was formed, and the metal oxide film 36 was removed after the oxidation annealing was performed at 350° C. Finally, the interlayer insulating layer 38 was formed above the interlayer insulating layer 34.
Sample J was formed under the same conditions as Sample I except that the thickness of the metal oxide layer 28 was set to 10 nm.
Next, the electrical characteristics of Sample I and Sample J were measured. The measurement conditions of the electrical characteristics of Sample I and Sample J are as follows.
It was shown that the threshold voltage of the semiconductor device is suppressed from shifting in both Sample I and Sample J, as shown in
Each of the embodiments and modifications described above as the embodiments of the present invention can be appropriately combined and implemented as long as no contradiction is caused. Furthermore, the addition, deletion, or design change of components, or the addition, deletion, or condition change of processes as appropriate by those skilled in the art based on each embodiment are also included in the scope of the present invention as long as they are provided with the gist of the present invention.
Further, it is understood that, even if the effect is different from those provided by each of the above-described embodiments, the effect obvious from the description in the specification or easily predicted by persons ordinarily skilled in the art is apparently derived from the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-058228 | Mar 2023 | JP | national |
